Rapid production apparatus (RPAs) form objects by sequentially forming thin layers, hereinafter “construction layers”, of construction material one on top of the other responsive to data, hereinafter “construction data”, defining the objects. There are numerous and varied types of RPAs and different methods by which they form the thin construction layers from which they build an object.
One type of RPA, conventionally referred to as an “ink jet RPA”, “prints” each layer of an object it builds. To form a given layer, the ink-jet RPA controls at least one dispenser, referred to as a “printing head”, to dispense at least one construction material (CM), hereinafter a “building material” (BM), in liquid form in a pattern responsive to construction data for the object and then solidifies the dispensed material. Generally, the layer is printed in the shape of a cross section of the object. Building material in adjacent, contiguous construction layers is printed in the shape of thin cross sections of the object that are displaced relative to each other by a small incremental distance along a same direction, hereinafter referred to as a “stacking direction”, relative to the object. The incremental distance is generally equal to the thickness of the layers.
For convenience of exposition, the cross sections of the object in whose shapes the construction layers are formed are assumed to be parallel to the xy-plane of a suitable coordinate system and the stacking direction is in the z-direction of the coordinate system. Optionally, the building material is a photopolymer, which is hardened after dispensing by exposure to suitable electromagnetic radiation, typically UV radiation.
For many construction objects, because of the complexity and/or shape of the objects, construction layers comprising only BM printed in the shape of cross sections of the construction objects are not completely self-supporting and require support during construction of the object. For such cases, at least one additional construction material CM, hereinafter referred to as “support material” (SM) is printed as required in suitable regions of each layer, to provide support for the building material in following layers. The support material and/or a shape in which it is formed, is such that upon completion of the object it can be removed from the object without substantially damaging the building material. In some embodiments, the support material, like the building material, is also a photopolymer.
An ink jet type of RPA typically comprises at least one ink jet printing head comprised in a “printing head block” that is mounted to a “shuttle”. Each printing head has an array of one or more output orifices and is controllable to dispense construction material, BM and/or SM, from each orifice independently of dispensing construction material from the other orifices. The construction material generally comprises one or more types of photopolymer materials typically stored in at least one supply cartridge. A suitable configuration of pipes and pumps transports the material or materials from the at least one supply cartridge to one or more reservoirs in the printing head block from which the at least one ink jet printing head receives the construction material. Optionally, to maintain appropriate viscosity of the at least one photopolymer, a controller controls at least one heater, optionally mounted to the printing block, printing head and/or reservoir, to heat the photopolymer to a suitable operating temperature. The one or more types of photopolymers may, generally, be dispensed in any combination, separately or together, simultaneously or consecutively.
During construction of an object, a controller controls the shuttle to repeatedly move over a support surface, hereinafter a “construction platform”, parallel to the x-y plane on which the object is formed by the RPA. The support surface and shuttle are generally housed in an at least partially enclosed “construction hangar” that protects the object while it is being built. As the shuttle moves, the controller controls each printing head to dispense construction material selectively through its orifices responsive to construction data defining the object, to print one construction layer of the object on top of the other on the construction platform.
Optionally, in moving the shuttle over the support surface during production of a construction layer, the controller controls the shuttle to move back and forth along a “scanning direction” conventionally defined as the x-direction. Optionally, at any one or more reversals of the shuttle along the x-direction, the controller increments displacement of the shuttle in a direction perpendicular to the scanning direction, in a direction referred to as “displacement” direction, conventionally the y-direction. Following production of a given construction layer, either the construction platform is lowered or the shuttle raised, along the stacking direction by a distance equal to a thickness of a next construction layer to be produced over the just formed given layer.
Mounted to the shuttle, adjacent to the printing head block are one or more sources of electromagnetic radiation, optionally UV radiation, for curing the photopolymer construction material printed in each construction layer. Also, optionally, mounted to the shuttle adjacent to the at least one printing head block is a “leveling roller” which levels newly printed layers of construction material to a predetermined layer height by removing surplus material from the layer. The surplus material removed from the layer is wiped off the roller by a “cleaning wiper” and gathered in a waste container comprised in the shuttle. Alternatively, the support surface moves.
Configurations of ink jet type RPAs are described in U.S. Pat. No. 6,193,923 (Leyden), U.S. Pat. Nos. 6,259,962, 6,658,314, 6,569,373, 6,850,334 and U.S. application Ser. Nos. 10/716,426, 10/336,032 and PCT Publication WO 2004/096527, the disclosures of which are incorporated herein by reference.